1. Field of the Invention
This invention relates to an antilock brake system in an automobile which prevents wheels from becoming locked upon emergency braking or when braking on a slippery road by adjusting a pressure of a brake fluid, and more particularly to a hydraulic power unit integrally mounting an electronic unit containing an electronic control section in the antilock brake system.
2. Statement of the Prior Art
There is known an antilock brake system which prevents the wheels in an automobile from being locked during emergency braking or braking on a slippery road, as a system for enhancing the safety of an automobile. Recently, automobiles provided with such an antilock brake system have become common place.
For convenience of explanation, a conventional antilock brake system will be described below by referring to FIGS. 10 and 11. FIG. 10 is a schematic explanatory view of the prior antilock brake system in the automobile and FIG. 11 is a diagram showing the electrical system of the antilock brake system.
As shown in FIGS. 10 and 11, a conventional antilock brake system comprises rotation detectors 1 to 4, a hydraulic power unit 195, an electronic control section 106 and a relaybox 107.
The rotation detectors 1 to 4 are provided on wheels A to D respectively to detect a rotating condition thereof. The rotation detectors 1 to 4 are provided with 1a to 4a and sensor rotors 1b to 4b, respectively. The sensors 1a to 4a are made of, for example, a permanent magnet, a coil, or a pole piece. The sensor is attached to a steering knuckle at the front wheel and to a hub spindle at the rear wheel. On the other hand, each of the sensor rotors 1b to 4b is provided on the outer periphery with serrations (not shown) formed uniformly along the peripheral direction. The sensor rotor is attached to a drive shaft at the front wheel and to a rear hub at the rear wheel. Accordingly, sensor rotors 1b to 4b rotate together with the wheels A to D, respectively. The sensors 1a to 4a detect the rotating condition of the wheels A to D by sensing the serrations on the outer periphery of the sensor rotors 1b to 4b during their rotations. The rotation detectors 1 to 4 transmit detecting signals from the sensors 1a to 4a to an electronic control section 106 to be described hereinafter.
The hydraulic power unit 105 is provided with four solenoid valves 105a to 105d for corresponding wheels. The hydraulic power unit 105 controls on-off operations of the solenoid valves 105a to 105d in accordance with control signals from the electronic control section 106, thereby controlling the pressure of a brake fluid supplied to wheel cylinders of the wheels A to D.
The electronic control section 106 receives the detecting signals from the rotation detectors 1 to 4 and monitors whether or not there is any wheel in a direction to be locked when it is braked in accordance with the detecting signal. The electronic control section 106 is made of a printed circuit plate. In the case that there is a wheel in the direction to be locked, the electronic control section 106 controls the hydraulic power unit 105 so that the pressure of brake fluid supplied to the wheel cylinder of the corresponding wheel is decreased. In the case that possible locking of the corresponding wheel is avoided, the pressure of brake fluid is increased again.
A relay box 107 contains motor and fail-safe relays 107a and 107b which amplify the control signal from the electronic control section 106 and applies the amplified control signal to the hydraulic power unit 105.
In FIG. 11, 108 is a battery for an automobile as a power source for the antilock brake system, 109 an ignition switch, 110 a stop lamp switch disposed in the vicinity of a brake pedal, 111 a stop lamp constituting a part of a rear lamp, 112 a warning lamp for indicating an abnormal state in the antilock brake system and 113 a diode for lighting the warning lamp 112 when the connector of the electronic control section is in a disengaged position or the fail-safe relay 107b is turned off.
In the prior antilock brake system, the hydraulic power unit 105 and relay box 107 are disposed in an engine compartment as shown in FIG. 10. On the contrary, the electronic control section 106 is generally disposed in a car interior such as a space under a seat or within front panel. The rotation detectors 1 to 4 are provided on the wheel sections as described before.
In modern automobiles, the number of electronic control sections is increasing in keeping with an increase in performance while at the same time, maintaining the interior of cars as spacious as possible is desirable. However, providing the electronic control section 106 in a car interior requires long wire harnesses to connect the rotation detectors 1 to 4 in the engine compartment to section 108.
Further, since the hydraulic power unit 105 in the engine compartment is provided separate from the electronic control section 106 in the car interior in the prior system, it is necessary to provide wire harnesses which electrically interconnect them as well. This lowers the efficiency of automobile production. In particular, since modern automobiles are provided with many systems which have not been provided in the conventional automobile, as well as antilocking braking systems, the number of wiring steps has increased and harness design has become very complicated. Accordingly, decreasing the number of wiring steps is desirable in order to simplify automobile production.